Various means have been attempted to provide an air foil for the mainsail of a sailing vessel such as the wrapping of a sail about the mast so that there will be a smooth curved aerodynamic lee side of the sail to prevent disrupting wind eddies at the mast where the sail is all in one smooth section from the mast to its leech as in U.S. Pat. Nos. 2,077,685 or 2,107,303 or by sections added to the mast as in U.S. Pat. No. 2,561,253. In U.S. Pat. No. 2,561,253 generally horizontal battens are utilized to shape the mainsail and this is also shown in U.S. Pat. No. 3,381,647. As for the furling, sails have been furled on a vertical axis within a fixed mast and aft of a fixed mast, without the provision of the aerodynamic means just referred to, such as in U.S. Pat. Nos. 3,749,042; 3,835,804. The sail in U.S. Pat. No. 2,107,303 is wrapped about the outside of the mast by rotating the mast.